children aged 5 to 12 can fly by themselves when they apply for unaccompanied children service, and they can fly by themselves when they are over 12. In order to ensure the safe and smooth flight of unaccompanied children, children who travel alone at the age of 5 but under the age of 12 must go through the relevant procedures for unaccompanied children before airlines can accept transportation. Aircraft: refers to a heavier-than-air aircraft that has one or more engines to generate forward thrust or pull, and the fixed wings of the fuselage to generate lift and fly in the atmosphere. The airplane is one of the most important inventions in the early 21th century, and it is generally acknowledged that it was invented by the American Wright brothers. Their flight on February 7, 1913 was recognized by the International Aviation Federation as "the first controlled sustained power flight by heavier-than-air aircraft", and in the same year they founded Wright Aircraft Company. Since the invention of the airplane, it has increasingly become an indispensable tool of modern civilization. It profoundly changed and influenced people's lives and opened the history of people conquering the blue sky.